Vapor Containment and Electrical Power Generation

ABSTRACT

A fuel vapor and energy conservation system includes one or more liquid fuel storage tanks connected to at least one fuel dispenser for delivering liquid fuel to vehicle fuel tanks and a motor/generator set powered by the evaporated fuel vapor and/or liquid fuel, used alone or in combination to generate electrical power. In some implementations, the fuel vapor and energy conservation system also includes a vapor conservation system with a tank defining a tank volume and a bladder disposed within the tank volume and defining a bladder volume for receiving fuel vapor from the ullage space, the tank and the bladder defining an air space external of the bladder, with a system of vapor conduit for conducting evaporated fuel vapor between the ullage space and the bladder volume and a system of air conduit for conducting air into and out of the air space external of the bladder.

This application is a continuation-in-part of U.S. application Ser. No. 11/744,541, filed, May 4, 2007, now pending, the complete disclosure of which is incorporated by reference herein.

TECHNICAL FIELD

This disclosure relates to underground fuel storage tanks, and more particularly to systems for containment and conservation of fuel vapor from such tanks, including for generation of electrical power.

BACKGROUND

Vehicle fueling service stations in some regions of the United States, i.e. those regions where only Phase I (i.e. non-Phase II) vapor recovery is mandated, and in many other countries, operate with limited or no restrictions on release of fuel vapors into the environment, e.g. including fuel vapors generated by evaporation of liquid fuel into the ullage space of vehicle and underground storage tanks, and then displaced from the tank by entering liquid fuel during filling. Even vehicle fueling service stations operating under the more stringent controls of Phase I and Phase II vapor recovery can under some circumstances, release fuel vapors into the environment.

When a service station dispenses gasoline to customer vehicles, the liquid gasoline level in the underground storage tank (“UST”) will fall. The space created in the UST as gasoline level falls produces a vacuum. This vacuum causes ambient air to enter the UST, e.g., via leaks in the tanks and the associated vapor piping network, including through the tank vent relief valve, if one has been installed. The inflow of air causes evaporation of liquid gasoline at the interface of liquid gasoline and air until an equilibrium condition is achieved. As the rate of gasoline sales diminishes, or when the service station closes for the night, evaporation of gasoline into the less-than-saturated air will continue, which causes the volume of gases in the vapor space to expand, raising the pressure in the UST vapor space. This condition leads to the loss of gasoline vapor to the environment, including through the same leakage paths that permitted ambient air to enter the UST ullage space during periods of negative pressure.

This loss of fuel in its vapor state is recognized as a detriment to the environment. Over an extended period of fueling operations, it can also represent a substantial loss of product, and loss of potential profit, to the service station owner and operator.

SUMMARY

According to one aspect of the disclosure, a fuel vapor and energy conservation system comprises a liquid fuel dispensing system comprising one or more liquid fuel storage tanks connected to at least one liquid fuel dispenser for delivering liquid fuel to vehicle fuel tanks, the one or more fuel storage tanks defining ullage space containing evaporated fuel vapor above an interface with liquid fuel; a vapor conservation system comprising a tank defining a tank volume, and a bladder disposed within the tank volume and defining a bladder volume for receiving fuel vapor, the tank and the bladder defining an air space external of the bladder; a system of vapor conduit for conducting evaporated fuel vapor between the ullage space and the bladder volume; a system of air conduit for conducting air into and out of the air space external of the bladder; and an electrical power generation system comprising a motor/generator set powered by at least the evaporated fuel vapor to generate electrical power.

According to another aspect of the disclosure, a fuel vapor and energy conservation system comprises a liquid fuel dispensing system comprising one or more liquid fuel storage tanks connected to at least one liquid fuel dispenser for delivering liquid fuel to vehicle fuel tanks, the one or more fuel storage tanks defining ullage space containing evaporated fuel vapor above an interface with liquid fuel; and an energy generation system comprising a motor/generator set powered at least by the evaporated fuel vapor to generate electrical power.

Preferred implementations of this aspect of the disclosure may include one or more of the following additional features. The fuel vapor and energy conservation system further comprises a vapor conservation system comprising a tank defining a tank volume, and a bladder disposed within the tank volume and defining a bladder volume for receiving fuel vapor from the ullage space, the tank and the bladder defining an air space external of the bladder; a system of vapor conduit for conducting evaporated fuel vapor between the ullage space and the bladder volume; and a system of air conduit for conducting air into and out of the air space external of the bladder.

Preferred implementations of both aspects of the disclosure may include one or more of the following additional features. The fuel vapor and energy conservation system further comprises a vapor shut-off and flow control valve disposed in a fuel vapor inlet conduit for regulating volume flow of evaporated fuel vapor to the motor of the motor/generator set; an air inlet valve disposed in an air inlet conduit for regulating volume flow of air to the motor of the motor/generator set; and an air/fuel ratio sensor disposed is an air and fuel vapor flow conduit in communication with the air inlet conduit and with the fuel vapor conduit; and an electrical controller; the air/fuel ratio sensor being disposed in electrical communication with the controller for signaling the ratio of air to fuel delivered to the motor; and the controller being in communication with the air flow control valve and the vapor shut-off and flow control valve for signaling adjustment of flow of air in the air inlet conduit and/or flow of evaporated fuel vapor in the fuel vapor conduit, thereby to adjust and maintain a desired ratio in a mixture of the fuel vapor and the air delivered to power the motor of the motor/generator set. The motor of the motor/generator set is selectively powered by liquid fuel and the system further comprises a liquid fuel shut-off disposed in a liquid fuel conduit in communication between a source of liquid fuel and a carburetor, the carburetor being disposed in communication with the liquid fuel conduit and the air intake conduit, and the controller being in communication with the air flow control valve and the liquid fuel shut-off for signaling adjustment of flow of air in the air inlet conduit and flow of liquid fuel in the liquid fuel conduit, thereby to adjust and maintain a desired ratio in a mixture of the fuel and the air delivered by the carburetor to power the motor of the motor/generator set. The motor/generator set is powered by evaporated fuel vapor and/or by liquid fuel, used alone or preferably in combination, to achieve a desired air/fuel ratio. The motor/generator provides power at least for operation of the vehicle fueling service station. The motor/generator provides power at least for delivery into a utility power grid. The system further comprises a starter and battery for initiating operation of the motor in the motor/generator set. The fuel vapor and energy conservation system further comprises an air filter disposed in the air inlet conduit. The fuel vapor and energy conservation system further comprises a flame arrestor in the fuel vapor conduit. The controller issues signals for activation and deactivation of the motor/generator set in response to at least one condition selected from among the following group of conditions: Phase 1 hose connection, UST vapor space pressure, manual start/stop button, and external power supply. The system of vapor conduit further comprises a conduit system for delivery of fuel vapor displaced from the ullage space by addition of liquid fuel to the one or more fuel storage tanks into the bladder volume, and for delivery of fuel vapor from the bladder volume back into the ullage space as liquid fuel is dispensed from the one or more liquid fuel storage tanks. The system of vapor conduit further comprises a conduit system for delivery of fuel vapor from the bladder volume back into the ullage space as liquid fuel is dispensed from the one or more liquid fuel storage tanks into vehicle fuel tanks over time. The system of vapor conduit further comprises a float check valve for restricting flow of liquid fuel toward the bladder volume. The system of air conduit further comprises a conduit system for delivery of the air displaced from the air space of the vapor conservation tank into the ullage space of a liquid fuel delivery vehicle, replacing a volume of liquid fuel delivered from the liquid fuel delivery vehicle. The system of air conduit further comprises a conduit system for delivery of the air displaced from the air space of the vapor conservation tank into the ambient environment. The bladder is inflatable and collapsible. The bladder is formed of thin wall, flexible material. The bladder is formed of resilient material.

According to still another aspect of the invention, a method of conserving fuel vapor in a liquid fuel dispensing system comprising one or more liquid fuel storage tanks connected to at least one dispenser for delivering liquid fuel to vehicle fuel tanks, a volume of liquid fuel dispensed from the one or more liquid fuel storage tanks being replaced by a volume of air, comprises connecting ullage space of the one or more liquid fuel storage tanks to a bladder within a vapor conservation tank; delivering liquid fuel into the one or more liquid fuel storage tanks, the liquid fuel displacing evaporated fuel vapor from the one or more liquid fuel storage tanks; delivering displaced evaporated fuel vapor into the bladder, the delivered evaporated fuel vapor inflating the bladder and displacing air from the air space of the vapor conservation tank external of the bladder; thereafter, over time, delivering evaporated fuel vapor from the bladder of the vapor conservation tank into ullage space of the one or more liquid fuel storage tanks, replacing the volume of liquid fuel delivered from the one or more liquid fuel storage tanks into vehicle fuel tanks; and using at least evaporated fuel vapor to operate a motor/generator set for generation of electrical power.

Preferred implementations of this aspect of the disclosure may include one or more of the following additional features. The method further comprises using at least a portion of the electrical power for operation of a vehicle fueling service station. The method further comprises contributing a portion of the electrical power to a local power grid. The method further comprises delivering liquid fuel from a liquid fuel delivery vehicle into the one or more liquid fuel storage tanks. The method further comprises connecting ullage space of the liquid fuel delivery vehicle to air space of the vapor conservation tank containing the bladder, external of the bladder; and delivering the air displaced from the air space of the vapor conservation tank into the ullage space of the liquid fuel delivery vehicle, the displaced air replacing a volume of the liquid fuel delivered from the liquid fuel delivery vehicle. The method further comprises delivering the air displaced from the air space of the vapor conservation tank into the ambient environment.

This disclosure thus describes a system for generation of electric power by use of gasoline vapor contained and conserved during normal operations of a vehicle fueling service station, e.g., by a vapor containment system described in my U.S. patent application Ser. No. 11/744,541. In one implementation, the gasoline vapors collected in the vapor containment bladder are optionally consumed as fuel in a gasoline motor/generator employed as an energy source to produce electric power for the benefit of the service station owner. The disclosed system will have application in service stations with both Phase I and Phase II vapor recovery equipment, and in those service stations with only Phase I vapor recovery equipment. The disclosed system will also have application in service stations without vapor recovery equipment, such as is the case in developing countries.

The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a somewhat diagrammatic representation of a typical (prior art) gasoline service station during a fuel “drop” or delivery, e.g. in the United States where only Phase I (i.e. non-Phase II) vapor recovery is mandated, and in other countries.

FIG. 2 is a somewhat diagrammatic representation of a Phase I gasoline service station of the type depicted in FIG. 1 during a fuel drop, the service station being equipped with one implementation of a fuel vapor containment system of the disclosure, the vapor containment tank being aboveground.

FIG. 3 is a somewhat diagrammatic side section view of a slightly different implementation of the fuel vapor containment system of FIG. 2 with an aboveground vapor containment tank.

FIG. 4 is a somewhat diagrammatic enlarged side section view of the bladder support assembly for the fuel vapor containment system of FIG. 3.

FIG. 5 is a somewhat diagrammatic representation of another implementation of a gasoline vapor containment system of the disclosure, the fuel vapor containment tank being underground.

FIG. 6 is an end view of the underground fuel vapor containment tank of FIG. 5.

FIG. 7 is a somewhat diagrammatic representation of the fuel vapor containment system of FIG. 5 during a fuel drop.

FIG. 8 is an end view of an underground fuel storage tank having a fuel inlet pipe terminating in the ullage space.

FIG. 9 is an end view of another implementation of a fuel vapor containment system of the disclosure with an underground fuel vapor containment tank.

FIG. 10 is a somewhat diagrammatic representation of a system for generation of electrical power including a motor/generator set selectively powered by fuel vapor, e.g. from a fuel vapor containment system of the disclosure, or by liquid fuel.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

Referring to FIG. 1, in a typical prior art fuel storage and delivery system 10, e.g. at a vehicle fueling service station, S, each underground storage tank 14 contains a volume of volatile liquid fuel 16, e.g. gasoline, and a volume of a saturated or semi-saturated mixture of gaseous fuel vapor and/or air 18 in a vapor or ullage space, U, above the liquid fuel. The ullage space is connected to the atmosphere via conduit 20, controlled by a UST pressure/vacuum relief vent valve 22, which typically is set to open at −8.0 inches W.C. to permit intake of air into the ullage space and to open at +3.0 inches W.C. to permit release of gaseous vapor from the ullage space, thereby to avoid dangerous buildup of pressure or vacuum within the UST 14.

During refueling of a vehicle, C, as liquid fuel, L, is delivered via conduit 24 from the UST 14 into the vehicle fuel tank 28, fuel vapor, V, displaced from the vehicle fuel tank by the liquid fuel is permitted to escape into the environment.

Bulk liquid fuel is delivered to service station, S, by fuel delivery vehicle, e.g. tanker truck 30. During a fuel “drop” or delivery, the truck tank is connected by conduit 32 to the fuel inlet spout 15 of UST 14, while the ullage space 18 of UST 14 is connected by conduit 36 to the ullage space 34 of the tanker truck. Delivery of liquid fuel 16 into UST 14, e.g. about 5,000 gallons delivered at 400 GPM (gallons per minute) is typical, causes displacement of fuel vapor 18 from the ullage of space, U, of UST 14, into the ullage space 34 of the tank truck, replacing the liquid fuel as it is delivered. Upon completion of the fuel drop, the tanker truck departs carrying 5,000 gallons of fuel vapor created from gasoline previously purchased by the service station owner, with the fuel vapor being subsequently displaced back into fuel company tanks as the tanker truck is filled for its next delivery.

Referring now to FIG. 2, according to the present disclosure, the fuel storage and delivery system 10′, e.g. at a gasoline fueling station, S′, is further equipped with vapor containment system 12 of the disclosure for capturing and retaining fuel, e.g. gasoline vapors, at a service station, e.g. rather than transferring the vapors for removal in a fuel tanker truck, as typically occurs at service stations with Phase I only vapor recovery, and/or rather than releasing all or a portion of those fuel vapors into the environment.

The vapor containment system 12 includes a vapor storage tank 42, e.g. an 8,000 gallon steel storage tank, connected to conduit 20, which, in turn, is in communication with the vapor space, U, of UST 14. The vapor space is controlled by pressure/vacuum relief vent valve 22, as described above. The storage tank 42 contains a thin wall, resilient, flexible urethane, inflatable bladder 44 defining an auxiliary vapor space volume 46 within the bladder, which is in communication with the UST vapor space, U, via conduit 20. The bladder 44 and the storage tank wall 48 also together define an air space 50 within the vapor storage tank 42 but external of the bladder 44, which is in communication with the atmosphere through a ⅛-inch orifice air relief/air ingestion port 52 to release air from the air space 50, and also to ingest air into the air space 50 at about 20 GPM when the pressure differential is 1 inch W.C., as described in more detail below. This is a passive system not requiring electrical components. As a result, installation costs are relatively low.

Referring also to FIGS. 3 and 4, and also to my U.S. Pat. No. 6,805,173, the complete disclosure of which is incorporated by reference herein, the vapor storage tank 42 is shown mounted in vertical position, e.g. upon a concrete tank slab 66. (Other suitable methods for installation and mounting may be employed.) The bladder 44 is suspended within the air space volume 50 of the tank 42 from the bladder support assembly 68. The support assembly includes a flange 70, secured to neck 71 at an aperture 72 into the tank volume by bolts 98 with lock washers 100 and nuts 102, sealed by o-rings 103, from which extends a pipe nipple 74 supporting a circumferential bladder flange 76. A clamp ring 78 bolted (79) to the bladder flange secures and seals the bladder opening. A tap 80 defines an inlet/outlet 81 to a first, axial vapor passageway 83 into the bladder volume 46 by way of pipe nipple 82 terminating in a pipe barb 84 and a siphon tube 85 that extends to the lower end of the bladder 44 within the tank 42. A tee-fitting 86 (to which tap 80 is mounted) defines an inlet/outlet 87 to a second, annular passageway 88 through the space between coupling 90 and pipe nipple 74 and the outer wall of pipe nipple 82. The inlets/outlets 81, 87, as well as condensate drain 92 from the base of the tank air space 50, are connected to conduit 20 by 1-inch connection piping 94. Flow through the connection piping 94 is controlled by ball valves 95, which should be padlock-secured against tampering. The air relief/air ingestion port 52 is connected to a pipe nipple 53 (FIG. 3) mounted to the flange 70 at an aperture 96 in communication with the air space 50 about the bladder 44 in tank 42.

In FIGS. 1 and 2, as described above, all three USTs 14 are employed for storage of liquid fuel, traditionally with the USTs 14, 14′ and 14″ respectively dedicated to storage of regular grade fuel, middle or mid grade fuel, and premium or plus grade fuel.

Referring also now to FIG. 5, in another, generally more preferred implementation, fuel storage and delivery system 10″ is upgraded for use with a Uni-hose dispenser system (not shown) that permits blending of regular grade fuel with premium or plus grade fuel from USTs 114 and 114′ to provide a blended middle or mid grade fuel at the dispenser 26 (FIGS. 1 and 2). As a result, the third UST 114″ is no longer utilized for storage of liquid fuel, making it available for use as a vapor storage tank 142 in a vapor containment system 112. The existing third tank, previously used to hold the mid-grade fuel product, is converted into a fuel vapor containment tank 142, in a vapor containment system 112, with an inflatable/collapsible bladder 144 for capturing and containing fuel vapor disposed within the underground tank. This alternative implementation typically provides relatively better economics, since it makes unnecessary installation of an additional aboveground tank and piping, e.g. as described with respect to FIG. 2.

According to this implementation, the third UST 114″ is retrofitted (typically after removal of the submerged turbine fuel pump (not shown) to provide maximum available volume) by installation of an inflatable/collapsible bladder 144, e.g., formed of thin wall, resilient, flexible material, e.g. urethane, defining an auxiliary vapor space volume 146 through the tank hatchway 130 (FIG. 5). The fuel vapor piping 120 is modified to place the ullage spaces, U, of USTs 114 and 114′ in communication with the auxiliary vapor space volume 146 of the bladder 144, e.g. via the former liquid fuel submerged turbine port pipe 115. The fuel vapor outlet pipe 117 from tank 114″, now in communication with the air space 150 defined between the bladder 144 and the storage tank wall 148, is placed in communication with the atmosphere through conduit 152, terminating at an air relief/air ingestion assembly 154, having a ⅛-inch orifice, again as described in more detail below. The piping connection between tank 114″ and the fuel vapor piping 120 is secured by valve 156, which is closed during normal operation. As in the implementation described above, this is a passive system not requiring electrical components. As a result, retrofitting and installation costs are relatively low.

Referring also to FIG. 6, and with reference to the above description of FIGS. 3 and 4, the bladder 144 is suspended within the air space volume 150 of the tank 142 from the bladder support assembly 168, through which extends former liquid fuel submerged turbine port 115, now connected to vapor conduit 120.

Referring again to FIG. 2, and more particularly to FIG. 7, in operation of the vapor containment system 112 of the disclosure, a fuel drop or delivery at a vehicle fueling service station, S′, with conservation of fuel vapor by the fuel station operator or owner, proceeds as follows:

1. With the bladder 144 in a collapsed condition, the driver of fuel tanker truck 30 makes a fuel hose connection (typically a 4-inch diameter hose 32) between the underground storage tank 114 and the tanker truck 30.

2. The driver makes a vapor hose connection (typically a 3-inch diameter hose 36) to the UST vapor connection pipe 119 in communication with the air space 150 of the vapor containment tank 114″, external of the bladder 144.

3. The driver opens the tanker vapor valve 301.

4. The driver opens the tanker liquid fuel valve 302.

5. The tanker truck 30 drops 5,000 gallons of liquid fuel 16 through conduit 32 and pipe inlet 15, into the UST 114, at a rate of up to 400 GPM, forcing 5,000 gallons of vapor 18 from the ullage space, U, of UST 114, through vapor conduit 120 and pipe inlet/outlet 115, into the auxiliary vapor space volume 146 of the bladder 144.

6. Inflation of the bladder 144 forces 5,000 gallons of air from the air space 150 between the bladder 144 and the wall 148 of UST 114″ through pipe inlet/outlet 119 and conduit 36, into the tanker 30.

7. The tanker 30 disconnects, replaces and properly secures the UST vapor connection sealing cap 118 on vapor connection pipe 119 (FIG. 5), and leaves, carrying 5,000 gallons of air.

8. Vehicles, C, are fueled with the 5,000 gallons of liquid fuel 16 delivered into UST 114, with removal of liquid fuel 16 from UST 114 drawing vapor 18 from the auxiliary vapor space volume 146 of bladder 144 into the ullage space, U, of UST 114.

9. Removal of vapor 18 from the bladder 144 into the ullage space, U, of UST 114″ causes gradual collapse of bladder, drawing air through conduit 152 and pipe 117, into the air space region 150 between the bladder 144 and the wall 148 of the UST 114″.

10. The entire process is repeated with each subsequent bulk delivery of liquid fuel 16.

Delivery of liquid fuel, e.g. gasoline, from the fuel tanker truck 30, at flow rates up to 400 GPM, into the underground storage tank 114 forces the fuel vapor 18 in the ullage space, U, of the underground storage tank 114 to flow through conduit 120, e.g. an underground 2-inch pipe, to inflate the bladder 144 in the vapor containment tank, i.e. aboveground tank 42 (FIG. 2) or underground tank 114″ (FIGS. 5 and 7), thereby forcing air in the space 150 between the bladder 144 and the inside tank wall 148 to flow out, and through the vapor hose 36 into the fuel tank truck 30.

The vapor space of the fuel tanker truck 30 is thus filled with air expelled from the air space 150 about the bladder 144 of the containment tank 114″, and the fuel vapor 18 displaced from the ullage space, U, of the underground storage tank 114 is contained with the bladder 144, remaining under control and possession of the service station.

The fuel vapor 18 that remains in the possession of the service station owner within the bladder 144 will subsequently, over time, be drawn back into the ullage space, U, of the underground fuel storage tank 114 as fuel is removed from the tank 114 to fuel customer vehicles, C. The air that would normally be ingested as the gasoline level in the underground storage 114 tank drops is now replaced by fuel vapor 18 from the bladder 144, resulting in essentially no loss of product due to evaporation.

The fuel vapor containment system (12, FIG. 2; 112, FIG. 5) may also provide storage capacity for containing and thereby preventing diurnal breathing losses. These losses occur due to fuel evaporation, as the fuel storage and delivery system (10′, FIG. 2, 10″ FIG. 5) moves to achieve equilibrium at the interface between liquid fuel 16 and vapor phase fuel 18 in the UST, and due to emissions related to changes in barometric pressure.

The potential savings that might be realized from use of a vapor containment system of the disclosure at a typical non-Phase II service station are as follows:

Annual Value of Vapor Retained:

Assume: Throughput: 100,000 gallons of fuel per month Gasoline savings rate: 0.15% Retail sales price: $3.00 per gallon Annual Savings due to retained vapor $\quad\begin{matrix} {= {100\text{,}000 \times 0.0015 \times 3.00 \times 12}} \\ {= {{\$ 5}\text{,}400\mspace{14mu} {per}\mspace{14mu} {year}\mspace{14mu} \left( {{at}\mspace{14mu} 100\text{,}000\mspace{14mu} {gallons}\text{/}{month}\mspace{14mu} {throughput}} \right)}} \end{matrix}$

Diurnal Breathing Loss Savings:

Assume: Positive pressure in the UST for 8 hours per day Vapor Growth Rate:  0.5 GPM Gasoline evaporated per gallon of vapor:  3.0 grams Given: Gasoline:  6 pounds per gallon Conversion 454 grams per pound Annual loss: (8 hrs/day) · (60 mins/hr) · (0.5 gpm) · (3 gms/gal)√(454 gms/lb)√(6.0 lbs/gal) · (365 days/yr) $\quad\begin{matrix} {= {96.5\mspace{14mu} {gallons}\mspace{14mu} {per}\mspace{14mu} {year} \times {\$ 3}{.00}\mspace{14mu} {per}\mspace{14mu} {gallon}}} \\ {= {{\$ 290}\mspace{14mu} {per}\mspace{14mu} {year}}} \end{matrix}$ Total Savings: $\quad\begin{matrix} {= {{{\$ 5}\text{,}400} + {\$ 290}}} \\ {= {{\$ 5}\text{,}690\mspace{14mu} {per}\mspace{14mu} {year}\mspace{14mu} {for}\mspace{14mu} {each}\mspace{14mu} 100\text{,}000\mspace{14mu} {gallons}\mspace{14mu} {of}\mspace{14mu} {throughput}\mspace{14mu} {per}\mspace{14mu} {month}}} \end{matrix}$ Annual Savings Annual Savings Annual Throughput at $3.00/gallon at $3.50/gallon 1,200,000 gallons per year  $5,690  $6,638 2,400,000 gallons per year $11,380 $13,276 4,800,000 gallons per year $22,760 $26,552

Fuel vapor generation and loss can be relatively higher under certain conditions. For example, referring to FIG. 8, in a UST 214, fuel inlet pipe 215 terminates in the upper region of the UST 214, i.e. in the ullage space, U, rather than, as preferred for minimizing fuel vaporization, in the lower region of the UST, and preferably below the level of the liquid fuel 16 in UST 214. The fuel spray 220 dropping through the ullage space, U, sharply increases the surface area interface of liquid fuel 16 to air/vapor 18 in the ullage space, U, thus increasing the rate of evaporation of liquid fuel 16 into fuel vapor 18.

Referring now to FIG. 10, an energy generation system 400 of the disclosure includes a motor 402 and a generator 404 coupled in a motor/generator set 406, e.g. a Guardian, Model 5244, available commercially from Norwall Power Systems, of Lake Havasu City, Ariz. After modification to employ a tri-fuel carburetor package capable of using gasoline, natural gas or propane as an energy source, this unit will provide 16 KW of power at 240 VAC, single phase. Depending on conditions at the vehicle fueling service station, S (FIG. 2), as described in more detail below, and/or decision by the service station operator or manager, the motor 402 is selectively fueled by gasoline vapor, e.g. from the vapor containment bladder 44 (FIG. 2), and/or by liquid gasoline from a liquid gasoline fuel source, e.g. from liquid fuel tank 408.

When the motor 402 is to be operated on liquid fuel from tank 408, liquid fuel shut-off valve 410 is opened by a signal 411 from the controller 420 (which is discussed in more detail below) to permit flow of the liquid fuel to carburetor 412, where it is combined with a flow of air from air inlet 414. The volume flow rate of air flowing from the inlet to the carburetor is regulated by air flow control 418, which is also operated by signals 419 from controller 420. An air filter 416 is preferably disposed in the air flow conduit, e.g. between the air inlet and the carburetor.

When the motor 402 is to be operated on fuel vapor from the vapor containment bladder 44 (and/or from the ullage spaces, U, of the USTs 14, 14′, 14″ (FIG. 2)), the fuel vapor is delivered through vapor conduit 422, where vapor shut-off and flow control valve 424 is opened and regulated by signals 425 from the controller 420 to permit a controlled volume of fuel vapor to flow toward the motor 402. When fuel vapors are used to power the engine 402, an air/fuel ratio sensor 426 monitors the air/hydrocarbon mixture and provides electronic signals 427 to the system controller 420, which in turn controls the vapor shut-off and flow control valve 422 and/or the air flow control 418 to adjust the flow of fuel vapor from the bladder 44 and/or the ullage space, U, mixed with the flow of ambient air from the inlet 414 to produce the desired fuel and air mixture. A flame arrestor 428 is preferably provided in the conduit 420, e.g. between shut-off and flow control valve 422 and the motor 402.

Operation of the motor 402 of the motor/generator set 406, fueled either by evaporated fuel vapor from the vapor conservation bladder 44 and/or from the UST ullage space, U, or by liquid fuel from tank 408, powers the generator 404 for generation of electrical power to be delivered by power lines 438 to the vehicle fueling service station, S, for its operating needs or into the local utility power grid for compensation or credit for the service station operator.

Upon detection of one of the following conditions, the controller 420 automatically issues a signal 431 to starter and battery set 430 mounted to motor 402, to actuate (turn on) the motor/generator set 406 to begin generation of electrical power:

1. When the vapor space pressure in the underground storage tanks (USTs 14, 14′, 14″) and/or in the vapor containment bladder 44 exceeds atmospheric pressure (i.e., +¼-inch W.C.), as communicated to the controller 420 by signal 432.

2. When a tank truck 30 (FIG. 7) concludes a fuel drop and the UST vapor connection sealing cap 118 is properly secured to UST vapor connection pipe 119 (FIG. 5), as communicated to the controller 420 by signal 434.

3. When an electric power failure occurs at the vehicle fueling service station, S, as communicated to the controller 420 by signal 436.

The motor/generator set 406 can also be manually started or stopped by electrical signal 436 to controller 420 transmitted by the service station operator or manager as needed or as otherwise dictated. When manually started, the motor may be operated on gasoline vapor from the vapor containment system 44 when the vapor space pressure in the underground storage tanks 14, 14′, 14″ is above +¼-inch W.C., or, when the pressure is below +¼-inch W.C., on liquid gasoline from the fuel tank 408 associated with the motor/generator set 406.

The motor/generator set 406 automatically deactivates (turns off) upon detection of, i.e. in response to signals indicating, one of the following conditions:

1. When the vapor space pressure in the ullage space, U, of the underground storage tanks and the fully collapsed vapor containment bladder 44 falls below atmospheric pressure (i.e., −¼-inch W.C.).

2. When the Phase I vapor connection sealing cap 118 is removed from the vapor connection pipe 119 (FIG. 5) of the underground storage tank 114″.

Operation of the electrical power generation system 400 of the disclosure will now be described in use with different generations of vehicle refueling service stations.

Service Stations with No Vapor Recovery:

When used in service stations without a vapor recovery system, the electrical power generation system 400 of the disclosure restricts discharge of fuel vapors to the atmosphere through fugitive emission leaks by controlling the UST vapor space pressure if the storage capacity of the bladder 44 at +¼-inch W.C. is exceeded. This condition could occur, e.g., if the barometric pressure were to drop rapidly. It could also occur, e.g., when the service station is shut down over night, as a result of continued evaporation of gasoline until equilibrium conditions occur.

When a tank truck 30 is actively refueling the service station, the vapor storage tank 42 (FIG. 2) provides temporary storage of the vapors displaced by the in-pouring gasoline. The stored vapor will then provide the fuel needed to run the motor/generator set 406 to produce electricity for operation of the service station, or if excess electric power beyond the needs of the service station is produced, the extra electricity can be delivered into the electrical power grid for credit from the local power utility.

Service Station with Phase I Vapor Recovery:

When used in service stations equipped with a Phase I vapor recovery system only, the vapor containment system restricts the transfer of gasoline vapor from the underground storage tank during a refueling drop by providing temporary storage for these vapors. In this case, the tank truck 30 will extract only air from the space 150 surrounding the bladder 144 in the bladder containment tank 114″. The gasoline saved in the form of vapor was produced from the gasoline previously purchased by the service station owner. The owner of the service station then can elect to use the captured vapors for the generation of electric power using the energy generation system 400 of the disclosure, or elect to allow the captured fuel vapor in the bladder to return to the underground storage tanks as liquid gasoline is dispensed to customers. This latter choice will prevent the evaporation of liquid gasoline that ambient air would cause since the vapor flowing back to the UST will contain sufficient hydrocarbon vapor to maintain an equilibrium condition without additional evaporation.

If the service station shuts down at night, and continued evaporation of gasoline is taking place, and/or barometric pressure drops causing the bladder to expand fully, the pressure could rise to +¼-inch W.C. When this occurs the motor/generator set 406 will start automatically to control the UST pressure and supply electric power for private use with excess electric power flowing to the utility grid for credit. In addition, the motor/generator set 406 is always available for emergency power generation.

Service Station with Phase I and Phase II Vapor Recovery:

When used in service stations with both Phase I & II vapor recovery, the electrical power generation system 400 of the disclosure has all of the advantages described above for service stations with Phase I only. The motor/generator set 406 in this application controls the UST vapor space pressure by turning on when the pressure reaches +¼-inch W.C. and turning off when the pressure falls to −¼-inch W.C., or to a lower negative pressure, providing it does not exceed the cracking pressure of the vent valve 22 (FIG. 2) (i.e., −8 inches W.C.).

In all of the above applications, the service station owner has two cost advantages for using electrical/power generation system 400. The gasoline vapor contained by the system can be used to generate electricity for their private use, or to reduce their cost for electric power by providing the excess electricity to the grid for a credit from the electric utility. The second practical advantage is the standby electric power generation provided whenever power failure occurs. This feature will allow the service station to continue to sell gasoline under power blackout conditions.

The disclosure offers both environmental and practical advantages. An environmental advantage is the effective control of the vapor space pressure in the underground storage tanks of any service station to minimize the escape of hydrocarbon vapor to the atmosphere by holding the pressure slightly above or below atmospheric. Under negative pressure conditions, ambient air will be drawn into the ullage space through leaks in the underground storage tanks and vapor piping system. This disclosure thus has application in service stations equipped with both Phase I and Phase II vapor recovery, and in service stations having Phase I only. The disclosure is equally beneficial in service stations in those countries that do not mandate the use of vapor recovery systems. The presence of an emergency back-up generator to keep service stations operating during periods of public power service interruption has both economic and public safety advantages.

A number of implementations of the disclosure have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. For example, the bladder described above may have other forms according to the disclosure. For example, the bladder may alternatively have the form of a resilient wall or a diaphragm.

Also, referring to FIG. 6, retrofitting of an existing, unused UST 114″ is preferred, e.g. as compared to use of an aboveground tank for the vapor control system, including for reasons of cost and security. However, service station USTs are typically protected by a relative thick, reinforced concrete pad 300, making modification of existing below-ground piping difficult and expensive, and thus preferably kept to a minimum. As result, where existing piping arrangements make retrofitting difficult or overly expensive, an aboveground vapor containment system 12, e.g. as described above with reference to FIG. 2, may be more viable.

Also, the submerged turbine pump in a retrofit UST, e.g. UST 114″ in FIG. 6, may be removed to allow room for expansion and contraction of the inflatable bladder 144 without unnecessary physical obstruction within the internal volume of the UST.

Additionally referring to FIG. 9, in some implementations, including those described above, in particular with respect to the implementations of FIGS. 5-7, a vapor conduit 120 connecting the ullage space, U, of UST 314 with the volume 346 of the bladder 344 in vapor containment tank 314″ may further include float check valve 380, or, in the alternative, float check valve 380′, for protecting the volume 346 of the inflatable bladder 344 from liquid fuel 16, e.g. in the event of a tank overfill during a fuel drop. In the alternative arrangement, the positioning of float check valve 380′ permits liquid fuel 316 from the truck overfill to drain back into the UST 314.

Also, for vehicle refueling service stations employing Phase I and Phase II vapor recovery, the vapor containment bladder system can optionally be omitted, while using the electrical power generation system 400 to control pressure of evaporated fuel vapor in the ullage space of the underground storage tanks.

Accordingly, other implementations are within the scope of the following claims. 

1. A fuel vapor and energy conservation system, comprising: a liquid fuel dispensing system comprising: one or more liquid fuel storage tanks connected to at least one liquid fuel dispenser for delivering liquid fuel to vehicle fuel tanks, the one or more fuel storage tanks defining ullage space containing evaporated fuel vapor above an interface with liquid fuel; a vapor conservation system comprising: a tank defining a tank volume, and a bladder disposed within the tank volume and defining a bladder volume for receiving fuel vapor, the tank and the bladder defining an air space external of the bladder; a system of vapor conduit for conducting evaporated fuel vapor between the ullage space and the bladder volume; a system of air conduit for conducting air into and out of the air space external of the bladder; and an electrical power generation system comprising a motor/generator set powered at least by the evaporated fuel vapor to generate electrical power.
 2. A fuel vapor and energy conservation system, comprising: a liquid fuel dispensing system comprising: one or more liquid fuel storage tanks connected to at least one liquid fuel dispenser for delivering liquid fuel to vehicle fuel tanks, the one or more fuel storage tanks defining ullage space containing evaporated fuel vapor above an interface with liquid fuel; and an electrical power generation system comprising a motor/generator set powered at least by the evaporated fuel vapor to generate electrical power.
 3. The fuel vapor and energy conservation system of claim 2, further comprising: a vapor conservation system comprising: a tank defining a tank volume, and a bladder disposed within the tank volume and defining a bladder volume for receiving fuel vapor from the ullage space, the tank and the bladder defining an air space external of the bladder; a system of vapor conduit for conducting evaporated fuel vapor between the ullage space and the bladder volume; and a system of air conduit for conducting air into and out of the air space external of the bladder.
 4. The fuel vapor and energy conservation system of claim 1 or claim 2, further comprising: a vapor shut-off and flow control valve disposed in a fuel vapor inlet conduit for regulating volume flow of evaporated fuel vapor to the motor of the motor/generator set; an air inlet valve disposed in an air inlet conduit for regulating volume flow of air to the motor of the motor/generator set; and an air/fuel ratio sensor disposed is an air and fuel vapor flow conduit in communication with the air inlet conduit and with the fuel vapor conduit; and an electrical controller; the air/fuel ratio sensor being disposed in electrical communication with the controller for signaling the ratio of air to fuel delivered to the motor; and the controller being in communication with the air flow control valve and the vapor shut-off and flow control valve for signaling adjustment of flow of air in the air inlet conduit and/or flow of evaporated fuel vapor in the fuel vapor conduit, thereby to adjust and maintain a desired ratio in a mixture of the fuel vapor and the air delivered to power the motor of the motor/generator set.
 5. The fuel vapor and energy conservation system of claim 4 wherein the motor of the motor/generator set is selectively powered by liquid fuel and the system further comprises: a liquid fuel shut-off disposed in a liquid fuel conduit in communication between a source of liquid fuel and a carburetor, the carburetor being disposed in communication with the liquid fuel conduit and the air intake conduit, and the controller being in communication with the air flow control valve and the liquid fuel shut-off for signaling adjustment of flow of air in the air inlet conduit and flow of liquid fuel in the liquid fuel conduit, thereby to adjust and maintain a desired ratio in a mixture of the fuel and the air delivered by the carburetor to power the motor of the motor/generator set.
 6. The fuel vapor and energy conservation system of claim 5, wherein the motor/generator set is powered by evaporated fuel vapor and/or by liquid fuel, used alone or in combination.
 7. The fuel vapor and energy conservation system of claim 1 or claim 2, wherein the motor/generator provides power at least for operation of the vehicle fueling service station.
 8. The fuel vapor and energy conservation system of claim 1 or claim 2, wherein the motor/generator provides power at least for delivery into a utility power grid.
 9. The fuel vapor and energy conservation system of claim 1 or claim 2, wherein the system further comprises a starter and battery for initiating operation of the motor in the motor/generator set.
 10. The fuel vapor and energy conservation system of claim 1 or claim 2, further comprising an air filter disposed in the air inlet conduit.
 11. The fuel vapor and energy conservation system of claim 1 or claim 2, further comprising a flame arrestor in the fuel vapor conduit.
 12. The fuel vapor and energy conservation system of claim 1 or claim 2, wherein the controller issues signals for activation and deactivation of the motor/generator set in response to at least one condition selected from among the following group of conditions: Phase 1 hose connection, UST vapor space pressure, manual start/stop button, and external power supply.
 13. The fuel vapor conservation system of claim 1 or claim 3, wherein the system of vapor conduit further comprises a conduit system for delivery of fuel vapor displaced from the ullage space by addition of liquid fuel to the one or more fuel storage tanks into the bladder volume, and for delivery of fuel vapor from the bladder volume back into the ullage space as liquid fuel is dispensed from the one or more liquid fuel storage tanks.
 14. The fuel vapor conservation system of claim 13, wherein the system of vapor conduit further comprises a conduit system for delivery of fuel vapor from the bladder volume back into the ullage space as liquid fuel is dispensed from the one or more liquid fuel storage tanks into vehicle fuel tanks over time.
 15. The fuel vapor conservation system of claim 13, wherein the system of vapor conduit further comprises a float check valve for restricting flow of liquid fuel toward the bladder volume.
 16. The fuel vapor conservation system of claim 1 or claim 3, wherein the system of air conduit further comprises a conduit system for delivery of the air displaced from the air space of the vapor conservation tank into the ullage space of a liquid fuel delivery vehicle, replacing a volume of liquid fuel delivered from the liquid fuel delivery vehicle.
 17. The fuel vapor conservation system of claim 1 or claim 3, wherein the system of air conduit further comprises a conduit system for delivery of the air displaced from the air space of the vapor conservation tank into the ambient environment.
 18. The fuel vapor conservation system of claim 1 or claim 3, wherein the bladder is inflatable and collapsible.
 19. The fuel vapor conservation system of claim 1 or claim 3, wherein the bladder is formed of thin wall, flexible material.
 20. The fuel vapor conservation system of claim 19, wherein the bladder is formed of resilient material.
 21. A method of conserving fuel vapor in a liquid fuel dispensing system comprising one or more liquid fuel storage tanks connected to at least one dispenser for delivering liquid fuel to vehicle fuel tanks, a volume of liquid fuel dispensed from the one or more liquid fuel storage tanks being replaced by a volume of air, said method comprising: connecting ullage space of the one or more liquid fuel storage tanks to a bladder within a vapor conservation tank; delivering liquid fuel into the one or more liquid fuel storage tanks, the liquid fuel displacing evaporated fuel vapor from the one or more liquid fuel storage tanks; delivering displaced evaporated fuel vapor into the bladder, the delivered evaporated fuel vapor inflating the bladder and displacing air from the air space of the vapor conservation tank external of the bladder; thereafter, over time, delivering evaporated fuel vapor from the bladder of the vapor conservation tank into ullage space of the one or more liquid fuel storage tanks, replacing the volume of liquid fuel delivered from the one or more liquid fuel storage tanks into vehicle fuel tanks; and using at least evaporated fuel vapor to operate a motor/generator set for generation of electrical power.
 22. The method of claim 21, comprising using at least a portion of the electrical power for operation of a vehicle fueling service station.
 23. The method of claim 22, comprising contributing a portion of the electrical power to a local power grid.
 24. The method of claim 21, further comprising: delivering liquid fuel from a liquid fuel delivery vehicle into the one or more liquid fuel storage tanks.
 25. The method of claim 24, further comprising: connecting ullage space of the liquid fuel delivery vehicle to air space of the vapor conservation tank containing the bladder, external of the bladder; and delivering the air displaced from the air space of the vapor conservation tank into the ullage space of the liquid fuel delivery vehicle, the displaced air replacing a volume of the liquid fuel delivered from the liquid fuel delivery vehicle.
 26. The method of claim 21, further comprising: delivering the air displaced from the air space of the vapor conservation tank into the ambient environment.
 27. The method of claim 21, comprising the further step of: connecting one or more underground storage tanks to a vapor conservation tank in the form of an auxiliary tank containing the bladder.
 28. The method of claim 21, comprising the further step of: connecting one or more underground storage tanks to a vapor conservation tank in the form of an aboveground auxiliary tank containing the bladder.
 29. The method of claim 21, comprising the further steps of: converting an underground storage tank to a vapor conservation tank containing the bladder; and connecting one or more underground storage tanks to the vapor conservation tank in the form of the converted underground storage tank containing the bladder. 